Method and apparatus for the manufacture of vulcanized fiber sheet materials



METHOD AND APPARATUS FOR THE MANUFACTURE OF VULCANIZED- FIBER SHEETMATERIALS Filed June 25, 1965 8- 7, 1968 w. J. BRENNAN 33 393'OUUUUUUUUU INVENTOR. WILLIAM J. BRENNAN ATTORNEY United States Patent3,399,093 METHOD AND APPARATUS FOR THE MANU- FACTURE 0F VULCANIZED FEBERSHEET MATERIALS William J. Brennan, Bridgeport, Pa., assignor to TheBudd Company, Philadelphia, Pa., a corporation of Pennsylvania FiledJune 23, 1965, Ser. No. 466,311 Claims. (Cl. 1S676) ABSTRACT OF THEDISCLOSURE A pair of rollers is provided to receive a vulcanized fibersheet material therebetween. One of the rollers is heated and the otheris cooled. The material is kept under tension as it leaves the rollers.

This invention relates to an improved method and apparatus for themanufacture of vulcanized fiber sheet materials. More particularly itconcerns a novel apparatus and method for calendering relatively thinvulcanized fiber sheet materials to remove and eliminate undulations ofportions of the material.

The term vulcanized fiber referred to herein denotes a tough, hornycellulosic material. Vulcanized fiber is made by treating substantiallycellulosic fibrous materials With a hydrolizing agent. The most commonlyused hydrolizing agent is zinc chloride. The hydrolizing agentgelatinizes the surfaces of the cellulosic fibers and the individualfibers adhere to each other. When the hydrolizing agent is leached fromthe cellulosic fibers, strong bonds develop between the individualfibers, and a tough, dense material is obtained.

The term bagginess as used herein denotes a condition that occurs insheet materials in which portions of the sheet become undulated orcorrugated. A sheet of baggy fiber has an overall appearance of beingwarped and somewhat wrinkled.

Vulcanized fiber is a relatively old material. It was the forerunner ofmany of todays modern plastics. Bagginess has been a constant problemconfronting vulcanized fiber producers since vulcanized fiber was firstintroduced almost a century ago. Bagginess makes it difficult, if notimpossible, to process the vulcanized fiber sheets in fabricatingoperations.

It has heretofore been proposed to form the vulcanized fiber underrelatively high tension in an attempt to pull out the bagginess.However, it was found that the use of the higher tensions aggravated thebaggy condition. It was heretofore proposed to use virtually no tensionin the manufacture of vulcanized fiber. This was also unsuccessful.Various combinations of high tension and low tension, and variations indrying conditions were attempted to correct the problem of bagginess.None of the methods suggested proved satisfactory.

Accordingly, it is the object of this invention to provide an improvedmethod and apparatus to produce fiat vulcanized fiber sheet material.

It is another object of this invention to provide a method wherebyundulations and corrugations of vulcanized fiber sheets can be removedand eliminated.

It is another object of this invention to provide apparatus to removeand eliminate bagginess from vulcanized fiber.

It is a further object of this invention to provide an apparatus andmethod to produce substantially fiat vulcanized fiber sheet materials.

It is a further object of this invention to provide a method andapparatus that with a minimum change of present operating procedureswill eliminate bagginess of vulcanized fiber sheet materials.

The other objects and advantages of the present invention will becomeapparent from the hereinafter detailed description and the appendedclaims when read in conjunction with the accompanying drawings in which:

FIG. 1 is a pictorial illustration of a sheet of bagg vulcanized fiber.

FIG. 2 is a schematic representation of an apparatus for the continuousformation of relatively thin vulcanized fiber sheet materials.

FIG. 3 is an enlarged illustration of the calender and wind-up reel asshown in the apparatus of FIG. 2.

FIG. 4 is an illustration of an alternative embodimerit of the apparatusof FIG. 3 having air convection means.

FIG. 5 is an alternative embodiment of the apparatus as illustrated inFIG. 3 having a cooling chamber.

It is to be understood that the forms of the invention herewithin shownand described are to be taken as preferred embodiments. In describingthe preferred embodiments of the invention illustrated in the drawings,specific terminology will be resorted to for the sake of clarity.However, it is not intended to be limited to the specific terms soselected, and it is to be understood that each specific term includesall technical equivalents which operate in a similar manner toaccomplish a similar purpose.

Turning now to the drawings, the number 10 designates the sheet of baggyvulcanized fiber of FIG. 1. The edges 12 of the sheet and the centerportions 14 are undulated. Because of the undulations, the baggy fibersheet material will not lie fiat in punching operations, and cannot becoated uniformly. Relatively thin vulcanized fiber sheet materials areespecially susceptible to becoming y- The relatively thin vulcanizedfiber sheets, that is sheets .005 to .125 inch thick, may bemanufactured in a continuous process utilizing the system of FIG. 2. Inthis process a ply, or plurality of plies 16, of substantiallycellulosic paper are fed through a concentrated zinc chloride solution18. The zinc chloride is absorbed by the paper. Excess zinc chloride isremoved by a set of nip rolls 20. The zinc chloride is permitted toreact on the cellulose in a reaction zone 22.

After a controlled amount of reaction has taken place, the zinc chlorideis removed from the plies in a series of steps in leaching tanks 24. Thepercent of the zinc chloride in the vulcanizing fiber is graduallyreduced until in the final tank 30 the vulcanized fiber containssubstantially no zinc chloride.

The vulcanized fiber can then be dried in an oven 33 where it issupported by a conveyor belt. The vulcanized fiber can then be furtherdried by passing it over a set of can dryers 32. The moisture content ofthe fiber is generally reduced to an amount above 4%, but below 10%. Thevulcanized fiber is then passed through calender 34 and reeled up forshipment.

The vulcanized fiber is advanced through the processing equipment bytension of one type or another. The plies when wet are easily stretchedand deformed, especially in the early stages of vulcanization.Non-uniform stretching of the sheet is believed to cause a portion ofthe bagginess.

In the vulcanization process, the plies shrink in both the machinedirection and the cross machine direction. This shrinkage produces acomplex combination of internal stresses in the vulcanized fiber.

Vulcanized fiber exhibits limited thermoplastic properties when itcontains moisture and is relatively warm. For the vulcanized fiber to bethermoplastic, it must contain at least 4% moisture by weight and be ata temperature above F. The thermoplastic properties of vulcanized fiberincrease with increases in temperature. In commercial practice it hasbeen found that the temperature of the fiber should be maintainedsubstantially above 120 F. and preferably in the range of l80-200 F. inorder to obtain the maximum utility of the thermoplastic property.

In the prior art processes the vulcanized fiber was dried to a moisturecontent above 4% and was packed relatively hot. Temperatures of thefiber as packed were often in excess of 160 F.

When the vulcanized fiber was packed, it exhibited a limited amount ofba'gginess. After remaining in storage for a week or so, the fiberbecame extremely baggy. This was due to the aforementioned internalstresses distorting the warm, moist thermoplastic vulcanized fiber.

It was initially believed that either reducing the moisture content orcooling the vulcanized fiber would prevent bagginess. This was anerroneous assumption. The bagginess that occurred in the vulcanizationprocess was sufiiciently great to impair the utility of the finalproduct. Neither reducing the moisture content or cooling the fiberreduced this bagginess. It was bound that it was not practical to reducethe moisture content sufficiently low to prevent bagginess because thefiber became brittle and quickly regained moisture from the atmosphere.

Accordingly, what was required was a method and ap paratus to remove thebagginess that developed during vulcanization and to control thestresses in the vulcanized fiber to prevent further development ofbagginess. This is obtained according to the teachings of this inventionby initially raising and maintaining the temperature of the vulcanizedfiber above 120 F., and preferably between 160200 F. whilesimultaneously forming the sheet into a fiat configuration. This initialstep removes the bagginess that is formed as a result of thevulcanization process. The heated flat vulcanized fiber is maintained ina flat configuration while it is cooled preferably below 120 degrees F.This second step sets or removes the internal stresses and preventsdevelopment of ba'gginess in storage.

An apparatus especially well suited to perform the above steps isillustrated in FIG. 3. The calendar stack 34 has a first roll 38 mountedin pressure contact with a second roll 40. Both the first and secondrolls 38 and 40 are substantially right cylinders. The rolls may have acertain amount of crown to correct bowing. Both rolls 38 and 40 arerigid and have surfaces that are free of undulations. The rolls providedflat surfaces against which the vulcanized fiber may be formed into afiat sheet. The rolls 38 and 40 are mounted to rotate on their axes. Therolls may be either free moving or driven.

The first roll 38 is heated. The roll may be heated by introducing andcirculating in the interior of the roll a heated fluid medium, forexample, superheated steam or a high temperature liquid. The temperatureto which the roll is maintained is dependent on certain factors. Theprimary function of the heated roll is to raise and maintain temperatureof the vulcanized fiber to between 120 F. and 200 F. The factors whichdictate how high the temperature of the first roll 38 must be maintainedare the initial temperature of the fiber, the temperature to which thevulcanized fiber is to be heated, and the length of time that the fiberis in contact with the first roll. In most applications the temperatureof the first roll should be maintained at approximately 250 to 270.

The second roll 40 is cooled. The roll 40 may be cooled by introducingand circulating a cooling fluid medium within the interior of the roll.A primary function of the second roll 40 is to act as a heat exchangerremoving heat from the vulcanized fiber sheet. The temperature of thevulcanized fiber sheet should be reduced substantially. The temperatureshould be reduced at least twenty degrees, and preferably to atemperature below 120 F. Accordingly, the coolant must maintain the rollat a relatively low temperature. It has been found that in mostapplications the coolant must be maintained at a temperatureapproximately 0 F. to reduce the temperature of the fiber to anacceptable range.

In operation, a sheet of vulcanized fiber containing at least 4%moisture is passed about a substantial portion of the periphery of thefirst roll 38. While in contact with the roll 38, the temperature of thesheet is raised to and maintained at a first temperature above 120 F. Atthis first temperature condition and the moisture condition as noted,the sheet becomes plastic and conforms to the configuration of thesurface of roll 38. The bagginess which is a result of the vulcanizationprocess is thereby removed.

The vulcanized fiber sheet is then passed about a major portion of theperiphery of the second roll 40. The temperature of the vulcanized fibersheet is reduced while in contact with the surface of the second roll40. The fiber is set in a flat configuration by cooling it while incontact with the surface of the second roll 40. The temperature of thefiber should be reduced at least 20 degrees below the first temperatureand preferably to below 120 F. The take-up reel 36 provides sufficienttension to hold the vulcanized fiber sheet in contact with both rolls 38and 40 during the heating and cooling steps.

The most difficult step is cooling the vulcanized fiber. If theapparatus of FIG. 3 is utilized, substantially all of the cooling mustbe done by the second roll 40. The rate of production is somewhatlimited by this factor.

An alternative embodiment of the apparatus of this invention isillustrated in FIG. 4. In addition to the calendar stack 34 of theembodiment of FIG. 3, means 44 to convect air about the vulcanized fibersheet are provided. In the illustration, fans 44 are shown. Thisapparatus has several advantages over the apparatus of FIG. 3.

The vulcanized fiber sheet is held in a fiat configuration and under atension between the contact point of the first and second rolls 38 and40, and the take-up reel 36. By circulating cooling air about the fiberat this point, as illustrated in FIG. 4, it is possible to remove theheat from the vulcanized fiber sheet quickly and efiiciently. Using theapparatus of FIG. 4, the optimum results obtainable with the apparatusof FIG. 3 are achieved with increased speed and efiiciency of operation.

In situations where it is not possible or practical to use the airconvection means as shown in FIG. 4, an apparatus as shown in FIG. 5 maybe utilized. This apparatus is similar to the apparatus of FIG. 3, butcontains in addition to the calendar a cooling chamber 46.

The cooling chamber may be utilized to reduce the temperature of thevulcanized fiber sheet in a manner similar to the aforementionedconvection means. The vulcanized fiber sheet is held in a taut, fiatcondition as it passes through the chamber 46. The fiber is set in thisflat condition. The cooling chamber 46 is not as desirable as theconvection apparatus of FIG. 4 in that the cooling chambers are moreexpensive to purchase and more difiicult to maintain and use.

It is to be understood that the forms of the invention herewithin shownand described are to be taken as preferred embodiments. Various changesmay be made in the apparatus without departing from the scope or spiritof the invention. For example, calender stacks having more than tworolls may be used. In addition, combinations of stacks may be used inwhich one stack is heated and one stack cooled. These, and other similarembodiments, are within the scope of this invention.

Having thus described my invention, I claim:

1. A calendering apparatus for .005 to .125 inch thick vulcanized fibersheet materials capable of removing and impairing formation of bagginessin said material, the apparatus comprising in combination: means forfeeding a plurality of plies of substantially cellulos'ic paper througha concentrated zinc chloride solution whereby said zinc form vulcanizedfiber sheet material, means including leaching tanks for removing saidzinc chloride from said material, means for drying said material toreduce the moisture content below but greater than 4%, at least tworigid, temperature controllable, calender rolls, said rolls beingsubstantially right cylinders and being mounted to rotate about theiraxes and in pressure contact; means advancing said material about amajor portion of the peripheral surfaces and through the contact pointof said rolls; means introducing and circulating a heated fluid mediumwithin the interior of a first of said rolls and heating m-aintainingthe temperature of the material while in contact with the surface ofsaid first roll at a first temperature above 120 F.; means introducingand circulating a cooling fluid medium within the interior of a secondof said rolls; reducing and maintaining the temperature of said materialsubstantially below the said first temperature; means rotating the rollsin a heat exchange relationship with respect to said vulcanized fibersheet material; and means for maintaining said vulcanized fiber sheetmaterial under tension while it is in contact with said rolls.

2. An improved apparatus for continuous manufacture of .005 to .125 inchthick vulcanized fiber sheet material comprising means for feeding aplurality of plies of substantially cellulosic paper through aconcentrated zinc chloride solution whereby said zinc chloride isabsorbed by said paper to react therewith to form vulcanized fiber sheetmaterial, means including leaching tanks for removing said zinc chloridefrom said material, means for drying said material to reduce themoisture content below 10% but greater than 4%; a calendering apparatusadapted to remove and impair formation of bagginess of the vulcanizedfiber sheet material, said apparatus comprising in combination: at leasttwo, rigid, hollow, substantially right cylindrical rolls, said rolls'being mounted to rotate about their axes and in pressure contact; meanscausing said material to advance about a substantial portion of theperiphery and between the contact points of said rolls; meansintroducing and circulating a heating fluid medium within interior of afirst of said rolls raising and maintaining the temperature of thematerial contacting the surface of the said first roll at a firsttemperature above 120 F.; means introducing and circulating a coolingfluid medium within the interior of a second of said rolls to reduce thetemperature of the material contacting the surface of the said secondroll substantially below the said first temperature; means rotating therolls about their axes in a heat exchange relationship with respect tosaid vulcanized fiber sheet material; and means for maintaining saidsheet material under tension while it is in contact with said rolls.

3. A method for removing and impairing formation of bagginess invulcanized fiber sheet materials which comprises the ordered steps of:passing a plurality of plies of substantially cellulosic paper through aconcentrated zinc chloride solution to cause said zinc chloride to beabsorbed by said paper to react therewith to form a sheet of vulcanizedfiber, removing said zinc chloride from said sheet, drying said sheet toa point not less than 4% moisture 'by weight, advancing said sheet ofvulcanized fiber containing least 4% moisture by weight over asubstantial portion of the peripheral surface of a first, rigid, rightcylindrical roll, simultaneously heating and maintaining the sheet at atemperature above F., conforming said sheet to the configuration of saidfirst roll; compressing said sheet between said first roll and a second,rigid, right cylindrical roll; and advancing said sheet over asubstantial portion of the peripheral surface of said second roll,simultaneously reducing the temperature substantially below the saidfirst temperature; and maintaining said sheet under tension when it isbetween said first and second rolls.

4. A method for removing and impairing formation of bagginess invulcanized fiber sheet materials which comprises the ordered steps of:passing a plurality of plies of substantially cellulosic paper through aconcentrated zinc chloride solution to cause said zinc chloride to beabsorbed by said paper to react therewith to form a sheet of vulcanizedfiber, removing said zinc chloride from said sheet, drying said sheet toa point not less than 4% moisture by weight, advancing said sheet ofvulcanized fiber containing at least 4% moisture by weight over asubstantial portion of the peripheral surface of thefirst, rigid, rightcylindrical roll, simultaneously heating and maintaining the sheet at atemperature above 120 F. conforming the said sheet to the configurationof said first roll; compressing said sheet between said first roll and asecond, rigid, right cylindrical roll; advancing said sheet over asubstantial portion of the peripheral surface of said second roll,simultaneously reducing the temperature to a second temperaturesubstantially below said first temperature; and circulating cooling airabout said sheet, reducing said temperature of said sheet below saidsecond temperature; and maintaining said sheet under tension when it isbetween said first and second rolls.

5. The method of claim 3 wherein the said first temperature is above F.and below 200 F.

References Cited UNITED STATES PATENTS 2,385,916 10/1945 Hahn 118-693,189,515 6/1965 Phillips 161-269 2,251,890 8/1941 Montgomery 162-2062,318,111 4/ 1943 Steinberge-r 264-284 2,551,005 4/1951 Johnson 264-2842,631,954 3/1953 Bright 264- 3,004,296 10/1961 Snedeker 264-175 FOREIGNPATENTS 484,560 7/ 1952 Canada.

586,366 11/1959 Canada.

659,880 3/1963 Canada.

EARL M. BERGERT, Primary Examiner.

M. L. KATZ, Assistant Examiner.

